The present invention relates to an apparatus for adjusting or setting the track of rotor blades through remote control, especially for a helicopter during flight. Each rotor blade has a two-part, lengthwise adjustable control rod with a servomotor which is associated with the supply unit for rotor blade control. A receiving/transmitting device is provided, and in the control rod a control device (potentiometer) as well as a measuring device are installed which are operatively connected with an operating station which is provided with an indicator or monitor.
Prior to mounting the rotor blades on the helicopter, the blades, which rotate with the rotor hub, are checked in a simulated hovering flight on a rigid test stand which is firmly located on the ground. In so doing, using a stroboscopic method, the blade track is measured, and each rotor blade is optimally adjusted by means of a lengthwise adjustable control rod in conformity with the test readings.
However, during forward flight of the helicopter, aerodynamic forces act on the rotor blades and bring them out of track, as a result of which vibrations occur in the blade operating cycle which are transmitted to the entire helicopter. In order to stop these undesired vibrations, and to adjust the rotor blades to another track, the helicopter must be landed and when the rotor has stopped the control rod of one rotor blade at a time must manually be either lengthened or shortened. The helicopter can then resume flight. This process must be repeated until an optimum vibration behavior of the helicopter during flight is achieved; i.e. the length of all of the control rods of the rotor blades have been correctly adjusted.
In an apparatus of the aforementioned general type (German Patent No. 27 57 617), the supply unit for rotor blade control is arranged on the rotatable rotor hub. The source of energy, which is located in this unit and is a part of the drive system, is connected by means of lines, which extend externally of the control rod, with the servomotor which is accommodated in the control rod. The receiving/transmitting device for transmitting signals, such as control signals and measured values of the tensile and compressive forces which occur in the control rod, is also located on the rotatable rotor hub. Such an arrangement of the supply unit and of the receiving/transmitting device on the rotor hub cannot be utilized with all types of helicopters, because the possibility for mounting is not always present. Furthermore, the lines, which are located externally of the control rod between the servomotor and the supply unit, can be easily damaged or can produce an imbalance, thereby having an unfavorable effect on the adjustment operations.
The main object of the present invention consists in substantially further developing an apparatus for adjusting the tracking of rotor blades of the aforementioned general type in such a way that the spatial separation of the receiving/transmitting device, the source of energy which is located in the supply unit and the servomotor, which is arranged externally of this unit, is eliminated and their connections are at the same time simplified.